The present invention generally relates to metal melt-spraying and more particularly, to a method of manufacturing high precision metal molds superior in durability through utilization of a metal melt-spraying technique at ambient temperature as disclosed, for example, in Japanese Patent Publication Tokkosho 47-24859.
In the conventional methods of manufacturing metal molds by utilizing metal melt-spraying, for example, a model for a desired product is first prepared by gypsum or the like, and after spraying molten metal onto the surface of the model, said model is released to form a shell made of a layer of the sprayed metal, with the shell being further backed up or lined so as to prepare the metal mold.
The metal molds thus obtained by the known method as described above, however, have such disadvantages that they are not only inferior in durability, but tend to be subjected to strain or distortion during manufacture, and thus, it is difficult to obtain metal molds having accurate dimensions, with the finished metal molds requiring further repairing or corrections. Therefore, metals having a sufficient hardness can not be employed for the purpose, and the resultant metal mold thus obtained has been generally weak in strength and suitable only for manufacturing trial products at most.
The method of manufacturing metal molds through employment of the metal melt-spraying technique (referred to as ambient temperature metal spraying hereinbelow) disclosed in Japanese Patent Publication Tokkosho 47-24859 referred to earlier (or U.S. Pat. No. 3,901,441), has the drawbacks as described above, in spite of the advantages that metal molds of complicated configurations may be produced through a simple procedure in a short period of time with a consequent low cost. As a result of various tests and researches, it has been made clear that such drawbacks are attributable to the fact that heat storing action is present during the process in which metallic particles flying at ultra high speeds are accumulated to form a layer, while a blasting action is produced as the metallic particles at high speeds collide with each other, and thus, it is difficult on the whole to avoid generation of distortion or to remove the distortion thus formed, with the desired dimensions not being readily achieved. Moreover, since the metallic layer itself obtained here is not very high in strength, reinforcement thereof is necessary, but there has been developed no effective means for achieving the reinforcing effect without generation of distortion.